Conventional positive displacement rotary machines such as piston, gear, and vane type suffer from high impact forces due to engagement of the parts and unbalanced vane and piston inertia forces. This results in excessive noise and wear. Gear and vane devices also have inherently high leakage flow because of the line contact sealing. Although radial and axial piston types have surface contact sealing, much lower leakage flow, and no impact forces, their unbalanced inertia forces tend to make them noisy and produce vibrations particularly at high speeds. In addition, piston machines have higher weight to power ratio than rotary gear and vane devices.